Antistick coated, steel building sheet



Feb. 9, 1954 P. w. JENKINS ANTISTICK COATED, STEEL BUILDING SHEET FiledSept. 22, 1951 IN VEN TOR. 2:0/ hz dwz/m6 BY Patented Feb. 9, 1954 PaulW. Jenkins, Pittsburgh, Pa., assigner to H. H. Robertson Company,Pittsburgh, Pa., a corporation of Pennsylvania Application September 22,1951, Serial No. 247,853

2 Claims. (Cl. 117-85) -This invention relates to building materials andmore particularly to a building material having a bituminous or similarsurface which is normally characterized by some degree of tacklness andby a tendency to adhere to other surfaces placed in contact therewith.

One object of the invention is to provide a building material of thecharacter specified with a novel and highly efficient antistick layercovering and adhering to a normally tacky surface of the buildingmaterial.

` More specifically, an object of the invention is to provide aprotected metal article of the type illustrated in the United StatesPatents to Robertson and to Coffman Nos. 1,277,755 and 2,073,334, havingan antistick coatingmaterial possessing novel and superiorcharacteristics which render such protected metal articles more suitablefor their intended purposes than prior commercial forms of sucharticles.

With these general objects in View and such others as may hereinafterappear, the invention consists in the building material, in theprotected metal sheets, and in the antistick compositions hereinafterdescribed and particularly defined in the claims at the end of thisspecification.

In the drawing, Figs. 1 and 2 represent sectional views illustratingbuilding sheets of the type shown in said Robertson and Coffman patents,each being provided with the present antistick layer.

In order to successfully ship and handle the protected metal buildingsheets forming the subject matter of the Robertson and Coffman patentsabove referred to, it has been the practice to provide the outerbituminousweatherproofing coatings with antistick layers in order toprevent the sheets from adhering together during shipment, andparticularly during shipment in warmer climates, and in practice, theseprior antistick compositions have comprised either the coatingcomposition forming the subject matter of United States Patent No.1,904,341, or the antistick coating composition disclosed in the UnitedStates patent to Young and Jenkins No. 2,440,626.

While the water-soluble antistick coating compositions disclosed in saidPatents Nos. 1,904,341` and 2,440,626 are capable of performing theirprimaryantistick function in an efficient manner and without deleteriouseffects upon the underlying bituminous weatherproong coatings of theprotected metal sheets, nevertheless, after such sheets have beenerected it has been found from experience `that those exposed surfaces,such as the outer surfaces of the building sheets erected uponthefbuilding, 'whether as roofing or siding,

y remain in `a much better condition than the inner surfaces of thesheets which are not exposed to the weather. This has been found to bedue to the fact that the effect of the weather upon the outer surfacesof the sheet has been to wash away the water-soluble antistick film fromthe outer surface of the sheet so that after a shortperiod of time theouter surfaces or sheets become free from the antistick lm.

In contrast therewith, experience has proved that those surfaces of thesheets which are not exposed to the weather, such as the undersurface ofthe sheets employed as the roof or the inner surfaces of the sheetsemployed as siding, do not remain in as satisfactory condition as do theouter or exposed surfaces of the sheets. This has been found due to thefact that in industrial buildings, such inner or undersurfaces of thesheet are normally subject to wide variations of temperature andvariations in the humidity of the atmosphere within the building, bothof which tend to induce strain between the antistick lm and theunderlying bituminous coatings tov which the film is attached, andeventually checking, cracking, and alligatoring of the bituminouscoatings result.

Because of the fact that it is impractical to wash off the antistickfilm or otherwise remove the same from such inner surfaces of the sheetsprior to or after erection of the sheets on the building, it isextremely desirable to produce an antistick coating composition whichnot only is capable of functioning as a satisfactory antistick duringshipment and handling of the sheet but which also possesses a minimumtendency to disrupt the bituminous coating on the under or inner surfaceof the sheet after the same has been erected upon the building. Priorattempts to control the plasticity of water-soluble films, such as thealginates and the cellulose ethers referred to in said U. S. Patents1,904,341 and 2,440,626, so as to minimize the tendency of the films toinduce strains in the bituminous coatings, have relied upon the use ofplasticizers of the class of the polyhydric alcohols, such as glycerine,all characterized by a relatively high degree of hygroscopicity. Changesin moisture content in response to changes in humidity have beenaccompanied by variations in physical properties and dimensions of thefilms, all of which have been conducive to setting up stresses betweenthe film and the underlying coatings. Furthermore, suchfllmvcompositions have been subject to leaching l out of the plasticizerby movement of moisture into and out of the film, and' gradual reductionto the unplasticized stata` and as a result checking, alligatoring, andcracking of the bituminous coatings have resulted, diminishing thedurability and impairing the appearance of the inner surfaces of thesheets.

The present invention contemplates an improved antistiek compositionandv an improved building sheet providedl With the antistick compositionand is based upon the recognition of the importance of holding themoisture content l of the antistick lm to as constant a value aspossible. hlm-forming material, such as an alginate, either sodium orammonium alginate,- or one of the cellulose ethers or the like, and.prelerablymethyl.

cellulose, is combined with a plasticizing agent of Very lowhygroscopicity and in suchproportions that the moisture contentof' theresulting film over the normal range of humidity tobe encountered in thebuilding is no greater than that oi the film-forming material under suchconditions. v4In practica plasticizing agent. which may be used forthisv purposel may com- Prise one of the water-soluble polyalliiylenevglyeols arid/or the. mono-ether or mono-ester,y derivatives thereof. Theprincipal elyeolsofthis class which I may use comprise, the polyethyleneelyeols and. the Water-soluble copolymers of.' ethylene and propyleueslyools which are the subject oi U, S.. Patent. No. 2,425,845.. Amongthe. derivatives oi., suehrolyelyools which may be used, I prefer toemploy tbemouo-ethersof. such polyglyools with the C to Ci ellrauols.The ud Water-soluble copolymers of ethylene and propylene elyools, andderivatives thereof, are found, to ollera particularly advantageousoombinarios4 of properties, to wit, 4low hyeroseopioity.. low'vaporpressure, low solubilltyiu end lor bi,- tuminous rrlaterialsv low pourpoint', and high viscosity index. Typical of these copolymers which maybe employed are vthe members. ofthe 75-Hserle's (-dlols)y and theylio-HB series (meriobutyl ethers) of fluids, marketed under the trade.llame ofv Uoort Members of this water-solubleseries arecharacterized-.bylow-vapor press sure, lowsolubility in or for aliphatic hydrocarbone,and are only slightly hysrosoopio.v

The film deposited from. a. water solution. of` equal partsby weight ofmethyl cellulose and Ucon fluidrQf-HB-GGD. is cited as an example ofaneleotive autistick which. is reletively'ilree from tendency to distortthe bituminous surfaces forl which intendedr even after-long periods of.oouteetuiider.adverseconditions.

vA somewhat` lower, ratio oi. the "Ueon," fluid to methyl cellulosemight be employed and some. advantage is gained by increasing` theratioto, as',A much as vtwo parts-A of'plasticzer to1 011e. partl of methylcellulose. Variations `in, ratio of this, order have Lnotbeen found to.make any appreciable difference ineiectiveness of the films inpreventing sticking. While the Ucon fluid has. been rreferred to, asN aplasticiaer flor the methyl. cellulose, it is. rather obvious froxnthe,propor-4v tions that may be employed that both` ingredients. areeffective-in fullling the antistiek. iiinet.ibmL andthat. it would; be.equally proper to refer tor theeellulose ether as a thickeningforbodying. agent for the. polyalkylene glycol derivative,

Reierring new to tbe drawing, in Fie. 1 1 have illustrated fa building`material oi the, type., illus:l trailed iu. the Robertson. patent, abovereferred to.l vvhereirilc represents tliefmetal core sheet; l2.,l theenveloping asphaltie. .uroteetive-ffcoatinsi 14, the, adhering klayers.0i blouslllaterial.i Such as; asbestos felt; lo. thebituminous,weatherbroong coating; and. I8A the'V present antistick iilm.In

Accordingly, a Water-soluble antistickV 4 Fig. 2, I have illustrated thebuilding sheet of the type illustrated in the Coffman patent abovereferred to wherein I0 represents the metal core sheet having a layer 20of zinc or equivalent metal coating upon the core sheet I0, and bywhichthelayers I4 of*v asbestos felt arebonded to the metal core sheet.l0. The` asbestos felt layers I4 are provided With the envelopingbituminous Weatherproong coating I6 and the latter with the presentantistick lm I8.

The polyalkylene glycols and derivatives thereof of low hygroscopicitywould not ordinarily be selectedy asplastiolzers for water-solublecelluloseethers or alginates because of their relativelypoorcompatibility with such materials and the results obtained by theiruse have been quite unexpected; Y

inefficient antistick solution may be made by dissolving the followingin Water:

The alginates used maybe single salts, such as' sodium, potassium, orammonium alginatesor double salts, such as copper ammonium alginate orzinc ammonium alginate.

An example of an eflicient antistick composittion embodying a,vcellulose ether, such as methyl cellulose, may comprise the following:

Parts by' Weighty Methyl cellulose .V "7.7 2; A, polyallyleneglycol orderivative charac terizedv by low hygroseopicity 1, toe,

This antistiek composition may be applied inany convenient and desireddilution, even as low as 3% solids, and operatesnotforily as asatisfactory and efficient antistick but also one in which thedisadvantages above-enumerated with respectv to checking, all'igatoring,and cracking ofthe bituminous coating lli' are reduced to a mirlirrium,`and in practice eliminated'.

Having thus described vthe invention, wfhatfis claimed is:-

l. A- building sheet forr roofing andsiding-pur,-v poses, comprising aprotected steel core sheetA having-an outer protectivewaterprooiing.ebituminous coating characterized by a normally tacky'surface,- rand av film coveringv said tacky surface and comprising awater-soluble cellulose-ether and a plasticizer-therefor consistingA of`armoric-` alkyl ether of a, polyalkylene glycol, the alkyl?grouprhavingl-l to lY carbon atoms.

2. A building material as definedin claim l wherein the water-solublecellulose etherand thet water-soluble polya-lk-ylene glycoliic materialareA in the rati'ooii from l to 1/27-2 parts by weight.

PAUL W; JENKINS@ lteferences,` Cited in. the iile, ofy this patent,`

UNITED STATES s

1. A BUILDING SHEET FOR ROOFING AND SIDING PURPOSES, COMPRISING APROTECTED STEEL CORE SHEET HAVING AN OUTER PROTECTIVE WATERPROOFING,BITUMINOUS COATING CHARACTERIZED BY A NORMALLY TACKY SURFACE, AND A FILMCOVERING SAID TACKY SURFACE AND COMPRISING A WATER-SOLUBLE CELLULOSEETHER AND A PLASTICIZER THEREFOR CONSISTING OF A MONOALKYL ETHER OF APOLYALKYLENE GLYCOL, THE ALKYL GROUP HAVING-1 TO 4 CARBON ATOMS.